This invention relates to ophthalmic compositions for soothing and lubricating the mammalian eye. More particularly, it relates to an improved ophthalmic solution which can replace the normal tears in the eye of individuals who do not secrete enough tears.
The tears secreted by the tear glands in the mammalian eye provide a fluid layer over the surface of the conjunctiva and cornea of the mammalian eye. This film serves a number of purposes. The tear film lubricates the conjunctival membranes and cornea, keeps the cornea hydrated, and supplies nutrients to the cornea. When the tear secretion decreases due to some pathological condition or aging, there may not be enough lacrimal fluid to keep the cornea moist. When there is not enough lacrimal fluid, the continuous film which normally covers the cornea may be broken and "dry spots" appear which lead to inflammation and discomfort. This condition has been treated by periodically instilling into the eye a fluid to take the place of the natural tears. These artificial tear solutions are generally aqueous solutions containing water soluble polymers to provide the proper viscosity, surface-active agents to provide wetting properties, salts and buffers to adjust the tonicity and pH of the solution. Most of the commercially available artificial tear solutions have been either excessively viscous and, therefore, difficult to use or they do not form a sufficiently long lasting film because of their low viscosity. An artificial tear composition has now been discovered which has a superior film life time without being excessively viscous.